1. Field of the Invention
This invention pertains to electrical connectors, and more particularly to connectors for printed circuitboards which possess desirable programmability and testability features.
2. Description of the Prior Art
Printed circuitboard connectors, such as edge board connectors, have already been disclosed in the prior art, for example, in U.S. Pat. Nos. 2,875,425 and 3,131,017. However, edge board connectors are not suitable for use in many airborne military applications because they are susceptible to malfunctions when exposed to extreme environmental changes, e.g., vibrations and shocks. This is evidenced by the military specification which precluded their use, i.e., General Specification for Electronic and Airborne Equipment MIL-E-5400.
As a result, two-piece connectors have been fabricated that will satisfy the aforementioned military specification. The first piece of such connectors is a receptacle which can be attached to a double-sided circuitboard. The receptacle includes a plurality of apertures containing metallic leads which are attached to terminals on both sides of the printed circuitboard. The second piece of the connector is an insulated body containing a number of metallic elements including pins which extend to be received within the apertures of the receptacle in the manner described in U.S. Pat. No. 3,721,944. Once engaged within the receptacle the interconnections between the terminals on the two sides of the circuitboard are complete.
In military airborne signal processing equipment it is necessary to use two one-sided boards mounted back-to-back rather than one double-sided printed circuitboard. This is required so that the temperature of the circuit elements can be reduced either by convection by means of air forced between the boards or by conduction by means of a metallic heat sink placed between them. In such cases, the basic structure of the interconnection strip described in U.S. Pat. No. 3,721,944 can be used with such back-to-back boards but it would necessarily make connections between all terminals of the two boards.
Such connectors disclosed in the prior art are not suitable for many military applications where space and volume are at a premium. As circuit components have been fabricated in smaller sizes, more components are able to fit within the available space on any given circuitboard. The additional components have led to additional interconnections which have created a need for electrical connector with closer contact spacings. The prior art has developed receptacles with as little as .050 inch spacings between pins but such structures have not facilitated crossover connectors with such close spacing.
In certain military applications where performance is critical, testing is desired at frequent intervals and the speed with which a malfunction can be located may effect the success of the mission. The prior art does not offer adequate flexibility for efficiently testing a variety of connections between circuitboards. Neither does it provide adequate provisions for fault isolation when it becomes necessary to resolve the location of a malfunctioning device down to a few out of the hundreds of circuit components on two boards.
Accordingly, it is an object of the present invention to provide a crossover connector that will connect only a predetermined number of terminals from one circuitboard to those of the other board and at the same time provide a means for testing all of the terminals coming in contact with said crossover connector.
A further object is to provide a means for separating the circuits of two back-to-back bonded planar printed circuitboards in order to improve the fault isolation of the two boards.
It is a further object to provide a structure which will facilitate automatic testing.